I don't know if you'd want to go to the extra trouble to save some money but just in case... I read that the ingredients in Bayer Advantage II are exactly the same for dogs and cats. This can save you some money. Buy the 6 pack of large dog flea treatment and put the med from all the vials in a bottle. Give it to your cats in the proper dosage using a measured dropper. For my cats that is about 35 treatments.
Saves a lot of money. 6 month pack for large dogs is a little under $60 for me. If I bought the 6 packs for cats that 36 treatments would cost me about $300.
You can do the math and determine how much smaller cats and dogs need.
This only pertains to Bayer Advantage II. Unless you look at other products and determine otherwise. This product is what works for me.